fix(benchmark): stop MCP startup deadlock — drop script-only runners from the calibration library barrel

[cdeust]

Problem

The plugin's MCP server (prd-gen) deadlocks on every launch — it never answers the MCP initialize handshake, so the server fails to come up under Claude Code. Node prints Warning: Detected unsettled top-level await and no evidence.db is created.

Root cause

The calibration library barrel packages/benchmark/calibration/index.ts re-exports the script-only runners next to its library-safe oracle/stats seams:

• runCalibration, selectModeFromArgv (from ./calibrate-gates.js)
• runProductionCalibration (from ./calibrate-gates-production.js)
• runProductionFromCli (from ./calibrate-gates-production-cli.js)

Those modules are script-only — top-level await + FS writes — exactly as their own §2.2 layer-contract banner in calibrate-gates-production.ts documents.

@prd-gen/mcp-server imports this barrel (via build-conclude-opts.ts) only for the library-safe oracle dispatch (invokeOracle / OracleUnavailableError / OracleInput). But esbuild, bundling the server, must initialise every statically-reachable module — so the script island's top-level await runs at server startup and never settles, so server.connect() is never reached.

Authoritative import chain (esbuild metafile):

mcp-server/index → pipeline-tools → build-conclude-opts
  → @prd-gen/benchmark/calibration (barrel) → calibrate-gates-production (top-level-await island)

Fix

Stop the library barrel from re-exporting the script-only runners. They have no barrel consumers — the CLIs and their tests already import them directly from their own modules (e.g. ../calibrate-gates.js), so this is non-breaking. It simply honours the §2.2 script/library boundary those modules already declare. The library-safe oracle/stats seams the server actually uses are untouched.

Net diff: the barrel source + the regenerated committed bundle (mcp-server/index.js). packages/benchmark/dist is gitignored.

Verification

• esbuild metafile: the script island (calibrate-gates*) is no longer in the server graph.
• Regenerated bundle: zero top-level await remain in mcp-server/index.js.
• Runtime: the server now answers initialize immediately —
  {"result":{"protocolVersion":"2024-11-05","capabilities":{"tools":{"listChanged":true}},"serverInfo":{"name":"prd-gen","version":"0.1.0"}},...}
• Tests: pnpm vitest run packages/benchmark packages/mcp-server → 339 passed.

Follow-up (not in this PR)

Separately, the published plugin ships no node_modules, and the bundle externalises ajv (+ its dynamic ajv/dist/runtime/* requires) and better-sqlite3, so a fresh claude plugin install can't launch the server until deps are installed/hoisted. Worth addressing in a packaging PR (ship a postinstall, or a flat node_modules, or inline the validator).

🤖 Generated with Claude Code